[RFE] Add Serial number to Host model

[grafuls]

Is your feature request related to a problem? Please describe.
On the host object we want to be able to hold the service tag for the host.

Describe the solution you'd like
Add the property to the Host on models.py. Modify lshw2meta to pick the serial from the lshw output from the main node as "serial".
Pass the serial to the wiki inventory.